Hydraulic motors and the like

ABSTRACT

A radial-cylinder hydraulic motor in which a series of reciprocating pistons are arranged around an eccentric mounted on a drive shaft, has a novel eccentric construction, the eccentric comprising an annulus which is driven by the pistons, and opposed piston-and-cylinder devices which are based on said drive shaft carry the annulus towards and away from the axis of the drive shaft to vary the throw of the eccentric and thus the displacement of the motor. The piston-and-cylinder device which moves the annulus away from the shaft axis is preferred to have a larger effective working area than the piston-and-cylinder device which moves the annulus towards the shaft axis.

United States Patent 1191 Mason et a1.

[11] 3,828,400 14 1 Aug. 13, 1974 HYDRAULIC MOTORS AND THE LIKE [73] Assignee: Chamberlain Industries Limited,

London, England 22 Filed: Jan. 27, 1972 211 App]. No.1 221,366

[30] Foreign Application Priority Data Jan. 29, 1971 Great Britain 3532/71 [52] US. Cl. 91/497 [51] Int. Cl. F0lb 13/06, F04b 1/30 [58] Field of Search 91/497; 417/221, 273, 270

[56] References Cited UNITED STATES PATENTS 1,149,728 10/1915 Ciarlo 74/571 L 2,404,175 7/1946 Holden 417/221 2,836,120 5/1958 Navarro .417/273 3,036,557 5/1962 Kimscy 91/490 3,067,728 12/1962 Bordim 91/471 3,255,707 6/1966 91/497 3,354,786 11/1967 Bedford 91/487 3,732,037 5/1973 Carlson ..4l7/2l7 3,737,014 6/1973 Dalrymple 192/85 AT FOREIGN PATENTS OR APPLICATIONS 564,304 2/1958 ltaly 417/273 Primary Examiner-William L. Freeh Attorney, Agent, or Firm Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT A radial-cylinder hydraulic motor in which a series of reciprocating pistons are arranged around an eccentric mounted on a drive shaft, has a novel eccentric construction, the eccentric comprising an annulus which is driven by the pistons, and opposed pistonand-cylinder devices which are based on said drive shaft carry the annulus towards and away from the axis of the drive shaft to vary the throw of the eccentric and thus the displacement of the motor. The piston-and-cylinder device which moves the annulus away from the shaft axis is preferred to have a larger effective working area than the piston-and-cylinder device which moves the annulus towards the shaft axis.

8 Claims, 11 Drawing Figures PATENIEBAum 31914 3. 8 28 .400

was 1 or 6 PATENTED AUG 1 3 m4 SHEET 2 [)F 6 PATENIE AUG I 31974 SHEEI U UF 6 PATENTEU AUB13I974 3,828,400

SHEET 5 0F 6 PATENTEDA I 31974 3, 828.400

sum 6 OF 6 HYDRAULIC MOTORS AND THE LIKE BACKGROUND OF THE INVENTION This invention relates to a variable-throw eccentric device which has particular application to slow-speed radialcylinder hydraulic motors.

Hydraulic motors of the radial-cylinder type, such as de cribed in the specification of our British Pat. No. l,085,232 and marketed under our Trade Mark STAFFA, are usually powered by means of a pump driven by an electrical motor. It is possible to vary the speed and the power output of the motor by varying the delivery (i.e., the displacement) of the pump, but this involves the provision of a relatively large and expensive pump to provide adequate low-pressure delivery for motor conditions of high speed and low torque. The size of pump could, however, be reduced if the motor displacement could be varied, and it is an object of the present invention to provide a means for satisfactorily varying the motor displacement.

SUMMARY OF THE INVENTION According to the present invention there is provided a radial-cylinder hydraulic motor in which a series of reciprocatory pistons are arranged around an eccentric mounted on a drive shaft, characterised in that said eccentric comprises an annulus in driving connection with said pistons, and opposed hydraulically-operated piston and cylinder devices based on the drive shaft carry the annulus towards and away from the axis of the shaft to vary the throw of the eccentric and thus the displacement of the motor.

During operation of the motor the annulus tends to move to a position of maximum eccentricity; thus, it is desirable to increase the effective working area of the piston and cylinder device which acts to move the annulus towards the shaft axis.

The throw may be infinitely variable, or the annulus may be movable between two positions such as high and low or, alternatively, drive and neutral. The neutral position may be employed to allow freewheeling of the shaft, for example where free-fall is required in winching operations.

Alternatively, the annulus may be movable past the neutral (zero-stroke) position, thus enabling the motor to reverse rotation without altering the direction of supply of fluid flow. This would simplify some hydraulic circuits by the elimination of costly control valves.

It has been found possible, moreover, to accommodate the piston and cylinder devices in a crank-shaft eccentric of the same size as those in our existing hydraulic motors of the type mentioned above. This is of great practical importance as an existing motor can be converted simply by replacing the crank-shaft and adding the require supplementary hydraulic control and supply system, and little alteration to our existing production line is required.

It will be appreciated that the present invention is also applicable to radial-cylinder hydraulic pumps, and it is envisaged that the invention may have wider application, for example to steam engines, air compressors or other reciprocating mechanisms. Thus, in wider concept, the invention provides a hydraulic machine in which at least one reciprocatory piston is arranged in driving engagement with an eccentric mounted on a drive shaft, characterised in that said eccentric comprises an annulus in driving connection with said piston, and opposed hydraulically-operatedpiston and cylinder means based on the drive shaft are arranged to carry the annulus towards and away from the axis of the drive shaft to vary the throw of the eccentric and thus the displacement of the machine.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are axial and transverse sectional views, respectively, showing one form of variablestroke hydraulic motor crank-shaft with its twoposition eccentric in the full-stroke position;

FIG. 3 is a view corresponding to FIG. 1, but showing the zero-stroke position of the eccentric;

FIG. 4 is an axial sectional view showing a radialcylinder hydraulic motor incorporating a crankshaft as shown in FIGS. 1 and 2;,

FIG. 5 is a diagrammatic sectional view showing a DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 to 3 of the drawings, crank-shaft 20 is for use in a radial cylinder hydraulic motor, for example as shown in FIG. 4, and is mounted in at least two races of roller bearings 21, and an eccentric 22 is located between the bearing races.

In this construction, the eccentric 22 comprises a circular annulus 23 whose outer face is slidingly engaged bycon-rod slippers (34 in FIG. 4) and which is carried at the outer ends of opposed pistons 24, 25 which are urgedoutwardly into contact with the annulus 23 by positioning springs 26, and the pistons are slidable in cylindrical recesses 27, 28 formed in body part 29 of the shaft 20. The shaft section, as shown in FIG. 2, is formed with flat side faces 30 and side pads 31 are keyed to the annulus 23 by keys 32. The pads 31 are in sliding contact with the faces 30 and may be hydrostatically balanced, for example by means of recesses 33 supplied with high-pressure fluid through ducts (not shown) which are formed in the pads and are fed from bores 34C in the con-rod slippers 34B (FIG. 4).

The arcuate outer faces of the pistons 24, 25 are (optionally) formed with tongues 35 which enter a locating groove 36 in the inner face of the annulus 23.

As can be seen from FIGS. 1 and 3, hydraulic fluid is fed to the recesses 27, 28 from ducts 37, 38, respectively. The ducts 37, 38 are formed in part 39 of the body of the hydraulic motor, and feed into channels 40, 41 which open into bores 42, 43 in the shaft 20 to feed to the recesses 27, 28.

The channels 40, 41 may be sealed against leakage by rings 44 and the whole assembly of channels, rings and casing comprises, in effect, a slip-ring assembly 45. This assembly is at one end of the shaft 20 as shown in FIGS. 1 and 3, but may alternatively be at some other convenient position in the motor.

In operation of the hydraulic motor, the swept volume can be varied by varying the throw of the eccentric 22 which determines the stroke of the reciprocating pistons 34 (FIG. 4). The eccentric throw is varied by shifting the annulus 23 and this is effected by feeding differential fluid pressures to the recesses 27, 28 and so moving the pistons 24, 25 whichcarry theannulus.

As shown in FIGS. 1 and 2, high-pressure fluid is fed through duct 37 to move piston 24 outwardly, while lowpressure fluid is applied to piston 25. In this position of maximum throw of the eccentric, the driving torque produced by the action of the aforementioned slippers (343) on the outer face of the annulus 23 is transmitted, through pads 31 and faces 30, to the shaft which thus rotates.

FIG. 3 shows the position when high-pressure fluid is fed through duct 38 to piston 25, and low-pressure fluid is applied to piston 24. In this position, the annulus 23 abuts against the shaft body part '29 and is held concentric with the shaft 20 to produce a zero-stroke or neutral drive effect which permits freewheeling of the shaft 20.

In a modification, a spacer 46, shown in broken lines in FIGS. 1 and 2, may be provided to limit the inward movement of piston 24 and so provide for a minimumstroke, as opposed to a zero-stroke, position of the eccentric. Likewise, a similar spacer could be provided in recess 28 to limit the movement of piston and so reduce the maximum stroke.

The hydraulic fluid supply to ducts 37, 38 may be derived from the pump which drives the motor, or a separate auxiliary pump may be provided for this purpose.

The sizes of the pistons 24, 25 are determined by the pressure of the hydraulic supply available and must, of course, be sufficient to balance the driving force applied to the annulus 23. It will be noted that the diameter of piston 25 is slightly larger than that of piston 24. It has been found that, in low speed hydraulic motors of the present type, the shift of the annulus 23 requires the provision of two pistons, one (24) to increase .the eccentricity while the shaft is turning slowly or is stationary, and the other (25) to reduce the eccentricity. The hydraulic forces on the annulus which are to be overcome by these pistons vary during rotation of the crankshaft 20. The highest force to be overcome by piston 24 occurs when the annulus 23 is being moved from the concentric (free-wheel) position and, as the eccentricity increases, this opposing force decreases. Piston 25 is required to decrease the eccentricity at all shaft speeds, and the maximum force required occurs when the annulus is being moved from the maximum eccentricity position; as the eccentricity decreases, so does this opposing force. On average, the hydraulic forces (and any centrifugal forces) on the eccentric act to increase its stroke and, at high speeds, only piston 25 would be required to move the annulus. At low speeds, however, piston 24 may be necessary for moving the annulus to a position of greater eccentricity, in certain angular positions of the output shaft.

The functions of piston 24 could conceivably be performed by a spring powerful enough to overcome the force, and this would result in an uneconomically and unsuitably large form of eccentric (23). The provision of two pistons also has the advantage of improving response to a servo control ina motor having an infinitely variable eccentricity.

In the motor shown in FIG. 4, which is similar to that described in our aforementioned U.S. Pat. No. 1085232, the five radial cylinders 47 are fed through a pintle (distributor) valve 48 which directs hydraulic fluid to supply-and-return conduits 49. Pistons 34 in the cylinders 47 drive the eccentric through con-rods 34A formed with slippers 348 which are in sliding engagement with the annulus 23 and are hydrostatically balanced through bores 34C. The motor incorporates a crankshaft 20 as shown in FIGS. 1 to 3 but, as shown in FIG. 4 the channels 40, 4] are fed by ducts 50, 51 which are connected through a two-position control valve 52 to high-pressure supply 53 and to drain 54, respectively. The valve 52 is located externally of the motor casing.

It is of importance to note that the overall dimensions of the eccentric 23 are the same as those in our existing STAFFA motors which can be modified simply by replacing the crank-shaft 20 and inserting parallel-faced part 39 which is then connected through control valve to the hydraulic supply of the motor. Also, no change in the other components of the motor are required in our existing production line.

The control valve may be mounted on the motor casing or may be mounted remotely, and one valve may control more than one hydraulic motor. For example, one or more valves may be provided at the drivers controls in a vehicle having hydraulic wheel motors.

The crank-shaft 20 shown in.FIG. 5 is basically similar to that described in FIGS. 1 to 3, but the FIG. 5 arrangement provides for infinite variation of the stroke, between predetermined limits. For this purpose, a servo control system is provided.

In the servo control system a valve spool 55 is housed in a bore 56 in valve body 57. The spool 55 is urged to a central position by springs 58 and is formed with four lands which define chambers A, B, C, D, and E.

In operation, high-pressure fluid is supplied from one of the two motor-supply lines 59, through a shuttle valve 60 which selects the higher of the two line pressures. The higher pressure is then fed through a first restriction 61 to a conduit 52 which pressurises chamber E and extends, through slip-ring assembly 45, to relief valve 63. Relief valve 63 is loaded by a spring 64 whose compression depends on the degree of eccentricity of the annulus 23. The high pressure fluid from shuttle valve 60 also passes through a second restriction 65 to a manually-operable control valve 66 having a drain outlet 67, and through a further conduit 68 to pressurise chamber A. Thus, fluid pressures influenced by the valves 63 and 66 act in opposition on the valve spool 55. High pressure fluid from shuttle valve 60 also passes to the bore 56 through a conduit 69 to be fed selectively to the conduits 42, 43 and thus to piston 24 or piston 25, depending on the position of valve spool 55.

As shown in FIG. 5, the system is in a state of balance, with the lands on spool valve 55 closing the conduits 42 and 43; chamber C is also closed, and chambers B and D are open to drain (into the motor crank case) through conduit 70. If, however, the valve spool 55 is displaced, for example by increase in fluid pressure from conduit 68 due to a change in the setting of control valve 66 or, alternatively, by fluctuating external forces on the annulus 23, high pressure fluid is fed from chamber C to the appropriate conduit to move piston 24 or 25. As the annulus 23 is thus shifted to a position of greater or less eccentricity, the compression of spring 64 is altered to change the pressure in chamber A and the spool 55 gradually returns to its mid position. Restrictions 71 may also be provided to act as dash-pots and damp the movements of spool 55.

In the crank-shaft shown in FIG. 6, a piston rod 72 carries the annulus 23 and extends through aligned bores 73, 74 in composite body part 29 of the shaft 20. A piston member 75 secured to the rod 72, is movable within chamber 76 in the shaft body part, under the action of fluid pressures fed to the upper and lower compartments of the chamber, to vary the eccentricity of the annulus 23. In this case the upper length 72A of the piston rod has a diameter slightly larger than that of the lower length 72B, so that the effective area of the upper face of piston member 75 is less than that of the lower face. The piston member 75 is formed with parts 77 which co-operate with recesses 78 to producea dashpot effect.

Referring to FIG. 7, the annulus 23 is formed with recesses 80, 81 which receive complementary projections 82, 83 formed on the crowns of the opposed pistons 24 and 25. In this construction, the annulus is formed with inner flat faces 84 which directly engage the flat faces on the shaft body part 29 and thus eliminate the necessity for supplementary pads (31), as is also the case in FIGS. 5 and 6.

FIG. 8 shows a modification of the FIG. 7 construction, in which the opposed pistons 24, 25 are arranged around circular projections 90, 91 formed on the shaft body part 29 and the eccentricity of the annulus is varied by pressurising chambers 92, 93 through ducts 94, 95 which extend from bores such as 42, 43.

FIG. 9 shows an embodiment of the invention as applied to a radial-cylinder hydraulic motor of the type having piston-sleeves, e.g., as shown in British Pat. Specification No. 886,923. In FIG. 9, a pentagon 100 is interposed between the eccentric annulus 23, and five piston-sleeves 101 bear against flat outer faces 102 of the pentagon. The annulus 23 is rotated inside the orbiting pentagon 100 and the eccentricity of the annulus is controlled as in FIG. 8. In FIG. 9, however, fluid pressure supply ducts 103 extend axially and then laterally through the shaft body part 29 and thence through the annulus and, through ducts 104 in the pentagon 100, into successive piston-sleeves 101 which are continuously urged inwardly by compression springs 105 and are in sealing engagement with the faces 102.

FIG. 10 shows a crank-shaft 20 for use in a rotarycasing motor such as a wheel motor. The construction is similar to that of FIGS. 1 to 3 but, since the shaft 20 is stationary, the layout can be simplified and fluid can be fed directly to and through axial bores 130, 131 to the opposed pistons 24, 25. In the case. conversion of an existing motor would only require replacement of the crank-shaft and the provision of appropriate feeds to bores 130 and 131; the aforementioned part 39 (FIGS. 1 to 4) is not required.

FIG. 11 shows an alternative form of stationary or rotary crank-shaft having an eccentric whose throw is infinitely variable, between limits. In this case a servovalve device 140, which is similar to 55 in FIG. 5, is

housed between the opposed pistons 24 and 25 which are again urged outwardly by springs 26.

The servo-valve devices have been described above as being hydraulically controlled but the servo-valves can be operated by, for example, mechanical means, and it is also envisaged that the eccentric shift might be effected by mechanical or electrical means rather than hydraulically. The servo-valves may also be controlled by signals from devices sensing fluid pressure, fluid flow rate, torque, or speed, to provide automatic control of a particular function.

The constructions described above provide a radial cylinder hydraulic motor having variable displacement and thus meets the objects of the invention, for exam ple in reducing the required size of driving pump and also, in cases where zero-stroke is available, allowing for free-wheeling which greatly facilitates operations such as hoisting and lowering. Variation in the throw of the eccentric also provides a useful further control of the motor output, or the pump output when the present invention is incorporated in a hydraulic pump.

We claim:

1. A radial cylinder hydraulic motor comprising a casing, a drive shaft journalled in said casing; an eccentric within said casing and extending about said drive shaft; a drive from said shaft to said eccentric to drive said eccentric; said drive shaft having oppositely facing cylindrical recesses therein facing said ecentric; said casing having a series of radial cylinders therein opening towards said eccentric and a drive piston in each radial cylinder to rotate said eccentric and thus said shaft, opposed control pistons in said cylindrical recesses having engagement with said eccentric; fluid pressure passageways to said cylindrical recesses; and valve means to admit fluid under pressure to said passageways and cylindrical recesses at variable pressures to vary the throw of said eccentric and thus the displacement of the motor, said control pistons and cylindrical recesses having different diameters, the control piston moving the eccentric towards the shaft axis to decrease the eccentricity being of smaller diameter than the control piston which moves the eccentric away from the shaft axis to increase the throw of the eccentric.

2. The hydraulic motor of claim 1, in which the control pistons are effective to move the eccentric between drive and neutral positions and past a neutral position to a drive position, to enable the motor to reversely operate without altering the direction of supply fluid flow.

3. The hydraulic motor of claim 1 in which spring means cooperate with the control pistons to move the eccentric to various selected positions.

4. The hydraulic motor of claim 1 in which the means for driving the eccentric from the shaft comprise paral lel plane inner surfaces on said eccentric cooperating with plane surfaces on said shaft.

5. The hydraulic motor. of claim 1, wherein the fluid pressure passageways leading to said control pistons vary the eccentricity of said eccentric, and lead through said shaft and are sealed to said casing.

6. The hydraulic motor of claim 1, in which said valve means to admit fluid pressure to said passageways comprises a servo-control system providing infinte variation of the throw of said eccentric between zero and a maximum.

7. The hydraulic motor of claim 6, and further comprising a two-line pressure feed to said radial cylinders, and a shuttle valve selecting the higher pressure of the two-line feed and directing said higher pressure to said servo-control system.

8. The hydraulic motor of claim 7, in which a springloaded valve in said shaft relieves excess fluid from the pressure within said eccentric.

UNITED. STATES 'IPATEMA-OEFIC'ET I: I I CERTIFICATEOF CORRECTION Patent No; 3,828,400 Dated August 13. 1974 Inventor-(s) Edward Mason and Michael lain Young It is certified that error appears in the above-identified patent and that said Letters Patentare hereby corrected as shown below:

In the Abstract: line 11, change "larger" to read --smaller--.

In column 6, line 38, change "smaller" to read --larger--.

Signed and sealed this 14th day of January 1975.

(SEAL) Attest: V

McCOY M; "mason JR. 0; MARSHALL DANN Attesting Officer Commissioner of Patents FORM po'wso USCOMM-DC 60376-P69 

1. A radial cylinder hydraulic motor comprising a casing, a drive shaft journalled in said casing; an eccentric within said casing and extending about said drive shaft; a drive from said shaft to said eccentric to drive said eccentric; said drive shaft having oppositely facing cylindrical recesses therein facing said ecentric; said casing having a series of radial cylinders therein opening towards said eccentric and a drive piston in eaCh radial cylinder to rotate said eccentric and thus said shaft, opposed control pistons in said cylindrical recesses having engagement with said eccentric; fluid pressure passageways to said cylindrical recesses; and valve means to admit fluid under pressure to said passageways and cylindrical recesses at variable pressures to vary the throw of said eccentric and thus the displacement of the motor, said control pistons and cylindrical recesses having different diameters, the control piston moving the eccentric towards the shaft axis to decrease the eccentricity being of smaller diameter than the control piston which moves the eccentric away from the shaft axis to increase the throw of the eccentric.
 2. The hydraulic motor of claim 1, in which the control pistons are effective to move the eccentric between drive and neutral positions and past a neutral position to a drive position, to enable the motor to reversely operate without altering the direction of supply fluid flow.
 3. The hydraulic motor of claim 1 in which spring means cooperate with the control pistons to move the eccentric to various selected positions.
 4. The hydraulic motor of claim 1 in which the means for driving the eccentric from the shaft comprise parallel plane inner surfaces on said eccentric cooperating with plane surfaces on said shaft.
 5. The hydraulic motor of claim 1, wherein the fluid pressure passageways leading to said control pistons vary the eccentricity of said eccentric, and lead through said shaft and are sealed to said casing.
 6. The hydraulic motor of claim 1, in which said valve means to admit fluid pressure to said passageways comprises a servo-control system providing infinte variation of the throw of said eccentric between zero and a maximum.
 7. The hydraulic motor of claim 6, and further comprising a two-line pressure feed to said radial cylinders, and a shuttle valve selecting the higher pressure of the two-line feed and directing said higher pressure to said servo-control system.
 8. The hydraulic motor of claim 7, in which a springloaded valve in said shaft relieves excess fluid from the pressure within said eccentric. 